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Subject: media: usbvision: Fix invalid accesses after device disconnect Author: Alan Stern stern@rowland.harvard.edu Date: Mon Oct 7 12:09:04 2019 -0300

The syzbot fuzzer found two invalid-access bugs in the usbvision driver. These bugs occur when userspace keeps the device file open after the device has been disconnected and usbvision_disconnect() has set usbvision->dev to NULL:

When the device file is closed, usbvision_radio_close() tries to issue a usb_set_interface() call, passing the NULL pointer as its first argument.

If userspace performs a querycap ioctl call, vidioc_querycap() calls usb_make_path() with the same NULL pointer.

This patch fixes the problems by making the appropriate tests beforehand. Note that vidioc_querycap() is protected by usbvision->v4l2_lock, acquired in a higher layer of the V4L2 subsystem.

Reported-and-tested-by: syzbot+7fa38a608b1075dfd634@syzkaller.appspotmail.com

Signed-off-by: Alan Stern stern@rowland.harvard.edu CC: stable@vger.kernel.org Signed-off-by: Hans Verkuil hverkuil-cisco@xs4all.nl Signed-off-by: Mauro Carvalho Chehab mchehab+samsung@kernel.org

drivers/media/usb/usbvision/usbvision-video.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)

---

diff --git a/drivers/media/usb/usbvision/usbvision-video.c b/drivers/media/usb/usbvision/usbvision-video.c index cdc66adda755..62dec73aec6e 100644 --- a/drivers/media/usb/usbvision/usbvision-video.c +++ b/drivers/media/usb/usbvision/usbvision-video.c @@ -453,6 +453,9 @@ static int vidioc_querycap(struct file *file, void *priv, { struct usb_usbvision *usbvision = video_drvdata(file);

+ if (!usbvision->dev) + return -ENODEV; + strscpy(vc->driver, "USBVision", sizeof(vc->driver)); strscpy(vc->card, usbvision_device_data[usbvision->dev_model].model_string, @@ -1099,8 +1102,9 @@ static int usbvision_radio_close(struct file *file) mutex_lock(&usbvision->v4l2_lock); /* Set packet size to 0 */ usbvision->iface_alt = 0; - usb_set_interface(usbvision->dev, usbvision->iface, - usbvision->iface_alt); + if (usbvision->dev) + usb_set_interface(usbvision->dev, usbvision->iface, + usbvision->iface_alt);

usbvision_audio_off(usbvision); usbvision->radio = 0;